Still Working on the Carburetor

I still have a bit of hesitation off idle which I cannot fix. I've asked about it on a few Internet forums but have not found a solution.

I thought it could be the idle mixture screws. However, when I change them it has only a very, very small impact on vacuum. From what I've read, these should be set to where you get the highest vacuum reading.

Someone asked about a leak around the intake on one forum. I said I had already checked it using WD-40 around the intake but could not find any leaks. I walked out to look it over again today and found oil behind the rear intake seal. It was only a small amount and was not there two or three weeks ago.

I cleaned the oil off and took the car out for a 10 mile drive. When I made it home, I checked and there was no oil. I'm not sure if this would be responsible for the problem or not. Unfortunately, I would need to buy another $30 bottle of Mobile One synthetic oil and drain all the fluids again to fix this seal leak. At this rate, the supplies are going to cost more than the intake itself.